Synthesis, crystal structure and magnetic properties of Ln2–xSrxNiO4 ±δ solid solutions (Ln = La, Nd, Sm and Gd; 1.0 ⩽x⩽ 1.67)

Abstract

New members of the Ln_2–xSr_xNiO_{4 ±δ}(Ln = La, Nd, Sm and Gd) solid solution series have been synthesized for x1.0. The upper limit of x is ca. 1.6 for La and 1.67 for Nd, Sm and Gd. The tetragonal K₂NiF₄-type crystal structures of these phases have been Rietveld refined using X-ray powder diffraction data. Thermogravimetry shows nickel to be in the + 3 oxidation state. Magnetic susceptibility data reveal Curie–Weiss behaviour for temperatures in the range 6–300 K. An approximate phase diagram for the Ln_2–xSr_xNiO_{4 ±δ} system as a function of Ln³⁺ radius and x is presented.